Transmitting apparatus, transmitting method, receiving apparatus, and receiving method

ABSTRACT

The luminance atmosphere that the creator intends is excellently reproduced on the receiving end. The transmission video data is obtained by applying a predetermined opto-electrical transfer function to the input video data. The transmission video data is transmitted together with the luminance conversion acceptable range information about a set region in the screen. For example, a transmitting unit transmits a video stream obtained by encoding the transmission video data while inserting the luminance conversion acceptable range information into a layer of the video stream. The receiving end obtains display video data by applying an electro-optical transfer function corresponding to the predetermined opto-electrical transfer function to the transmission video data, and performing a luminance conversion process in each of the set regions independently in accordance with the luminance conversion acceptable range information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority Patent Application JP 2014-173898 filed on Aug. 28, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present technology relates to a transmitting apparatus, a transmitting method, a receiving apparatus, and a receiving method and, in particular, relates to, for example, a transmitting apparatus that transmits transmission video data obtained by applying a predetermined opto-electrical transfer function to input video data.

BACKGROUND ART

A High Dynamic Range (HDR) imaging service provides an image with a wide luminance range to the receiving end and reproduces the image on the receiving end while reflecting the creator's intention on the image. This achieves display and reproduction of an image approaching the perception of the human eye in nature.

NPL 1 discloses, for example, a technique for transmitting a video stream generated by encoding transmission video data obtained by applying a gamma curve to input video data with luminance levels from 0 to 100%*N (the N is larger than one).

The levels of peak luminance of monitors (CE monitors) in receiving devices vary depending on the device property, the placement of the backlight, or the design method of a display panel. In comparison to the master monitor used for creating a program, the CE monitor sometimes has too high or dark luminance. Thus, the CE monitor may fail to correctly reproduce the luminance atmosphere that the creator intends.

CITATION LIST Non Patent Literature

NPL 1: High Efficiency Video Coding (HEVC) text specification draft 10 (for FDIS & Last Call)

SUMMARY OF INVENTION Technical Problem

It is desirable to excellently reproduce the luminance atmosphere that the creator intends on the receiving end.

Solution to Problem

According to an embodiment of the present technology, there is provided a transmitting apparatus including:

a processing unit configured to obtain transmission video data by applying a predetermined opto-electrical transfer function to input video data, and

a transmitting unit configured to transmit the transmission video data together with luminance conversion acceptable range information about a set region in a screen.

According to the present technology, a processing unit provides transmission video data by applying a predetermined opto-electrical transfer function to the input video data. For example, the input video data is video data including high dynamic range (HDR) images having contrast ratios from 0% to 100%*N (the N is a number larger than one) and having a brightness exceeding the brightness of the white peak value of an existing low dynamic range (LDR) image.

A transmitting unit transmits the transmission video data with the luminance conversion acceptable range information about a set region in the screen. For example, the set region in the screen may be set in the unit of pixel or in the unit of block including a predetermined number of pixels. Alternatively, for example, the transmitting unit may transmit the video stream obtained by encoding transmission video data, and may further include an information inserting unit configured to insert the luminance conversion acceptable range information into a layer of the video stream.

According to the present technology, transmission video data is transmitted together with the luminance conversion acceptable range information about a set region in the screen as descried above. This enables the receiving end to excellently reproduce the luminance atmosphere that the creator intends.

Note that, for example, the transmitting unit according to the present technology may transmit the transmission video data together with the luminance conversion acceptable range information about the entire screen in addition to the luminance conversion acceptable range information about the set region in the screen. In such a case, the receiving end can converts the luminance of the region other than the set region in the screen in a luminance conversion process in accordance with the luminance conversion acceptable range information about the entire screen.

According to an embodiment of the present technology, there is provided a receiving apparatus including:

a receiving unit configured to receive transmission video data obtained by applying a predetermined opto-electrical transfer function to input video data together with luminance conversion acceptable range information about a set region in a screen; and

a processing unit configured to obtain output video data by applying an electro-optical transfer function corresponding to the predetermined opto-electrical transfer function to the transmission video data, and converting luminance of the transmission video data in a luminance conversion process in accordance with the luminance conversion acceptable range information.

A receiving unit receives the transmission video data together with the luminance conversion acceptable range information about the set region in screen. The transmission video data is obtained by applying a predetermined opto-electrical transfer function to the input video data. For example, the input video data is video data including High Dynamic Range (HDR) images having contrast ratios from 0% to 100%*N (the N is a number larger than one) and having a brightness exceeding the brightness of the white peak value of an existing Low Dynamic Range (LDR) image.

For example, the set region in the screen may be set in the unit of pixel or in the unit of block including a predetermined number of pixels. For example, the receiving unit may receive the video stream obtained by encoding transmission video data, and the luminance conversion acceptable range information may be inserted in a layer in the video stream. Thus, the processing unit may applies, for example, an electro-optical transfer function that is inverse to the predetermined opto-electrical transfer function to the transmission video data, and outputs video data of which luminance is converted in accordance with the luminance conversion acceptable range information in a luminance conversion process.

According to the present technology, the transmission video data is received together with the luminance conversion acceptable range information about the set region in the screen such that the output video data is obtained by converting the luminance of the received data in accordance with the luminance conversion acceptable range information in a luminance conversion process as described above. This enables the receiving end to excellently reproduce the luminance atmosphere that the creator intends.

Note that, for example, the receiving unit according to the present technology may receive the transmission video data together with the luminance conversion acceptable range information about the entire screen in addition to the luminance conversion acceptable range information about the set region in the screen such that the processing unit can convert the luminance of the regions other than the set region in the screen in accordance with the luminance conversion acceptable range information about the entire screen in a luminance conversion process.

Advantageous Effects of Invention

The present technology enables a receiving end to excellently reproduce the luminance atmosphere that the creator intends. Note that the effects described herein are examples consistently. The present technology is not limited to the examples. Furthermore, the present technology may include an additional effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an exemplary configuration of a transmitting and receiving system as an embodiment.

FIG. 2 is a block diagram of an exemplary configuration of a transmitting apparatus including the transmitting and receiving system.

FIG. 3 is a diagram of an exemplary display luminance characteristic of a master monitor.

FIG. 4 is a diagram of an exemplary opto-electrical transfer function (OETF);

FIG. 5 is a diagram of the head access unit of a GOP when the data is encoded with an HEVC encoding method.

FIG. 6 is a diagram of an access unit other than the head access unit of a GOP when the data is encoded with an HEVC encoding method.

FIGS. 7A and 7B are diagrams to describe that set regions in a screen is set in the unit of pixel or in the unit of block including a predetermined number of pixels;

FIG. 8 is a diagram of an exemplary configuration of a regional level mapping SEI message.

FIG. 9 is a diagram of another exemplary configuration of a regional level mapping SEI message.

FIG. 10 is a diagram of the contents of primary information in an exemplary configuration of a regional level mapping SEI message.

FIG. 11 is a block diagram of an exemplary configuration of a receiving apparatus including a transmitting and receiving system.

FIG. 12 is a diagram of an exemplary electro-optical transfer function (EOTF).

FIGS. 13A and 13B are diagrams of an exemplary display luminance characteristic of a CE monitor when the highest luminance display capacity DP of the CE monitor is higher than the highest luminance PL assumed in the master monitor.

FIGS. 14A and 14B are diagrams of an exemplary display luminance characteristic of a CE monitor when the highest luminance display capacity DP of the CE monitor is lower than the highest luminance PL assumed in the master monitor.

FIGS. 15A and 15B are diagrams of another exemplary display luminance characteristic of a CE monitor when the highest luminance display capacity DP of the CE monitor is lower than the highest luminance PL assumed in the master monitor.

FIG. 16 is a block diagram of another exemplary configuration of the transmitting and receiving system.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a configuration to implement the present technology (hereinafter, referred to as an “embodiment”) will be described in the following order.

1. Embodiment

2. Variation

1. Embodiment

(Exemplary Configuration of Transmitting and Receiving System)

FIG. 1 illustrates an exemplary configuration of a transmitting and receiving system 10 as an embodiment. The transmitting and receiving system 10 includes a transmitting apparatus 100 and a receiving apparatus 200.

The transmitting apparatus 100 generates a transport stream TS in MPEG-2 as a container to transmit the transport stream TS through broadcast waves or with packets on a network. The transport stream TS includes a video stream obtained by encoding transmission video data obtained by applying a predetermined opto-electrical transfer function to input video data.

For example, the input video data includes High Dynamic Range (HDR) images having contrast ratios from 0% to 100%*N (the N is a number larger than one) and having a brightness exceeding the brightness of the white peak value of an existing Low Dynamic Range (LDR) image. It is assumed herein that the level of 100% is a luminance level corresponding to a white luminance value of 100 cd/m2.

The luminance conversion acceptable range information about a set region in the screen and the luminance conversion acceptable range information about the entire screen is inserted in a layer of the video stream. The luminance conversion acceptable range information will be described in detail below.

The receiving apparatus 200 receives the transport stream TS transmitted from the transmitting apparatus 100 through broadcast waves or with packets on a network. The transport stream TS includes a video stream including encoded video data. The luminance conversion acceptable range information about a set region in the screen and the luminance conversion acceptable range information about the entire screen is inserted in the video stream as described above.

The receiving apparatus 200 obtains output video data by applying, for example, an electro-optical transfer function that is in inverse to the predetermined opto-electrical transfer function on the transmitting end to the transmission video data, and converting the luminance of the data in accordance with the luminance conversion acceptable range information in a luminance conversion process. In such a case, the luminance of the data only in the luminance conversion acceptable range is converted, for example, depending on the peak luminance of the monitor.

Exemplary Configuration of Transmitting Apparatus

FIG. 2 illustrates an exemplary configuration of the transmitting apparatus 100. The transmitting apparatus 100 includes a control unit 101, an HDR camera 102, an HDR opto-electrical transfer unit 103, a video encoder 104, a system encoder 105, and a transmitting unit 106. The control unit 101 includes a central processing unit (CPU) to control the operation of each of the components in the transmitting apparatus 100 in accordance with a control program.

The HDR camera 102 captures an image of an object and outputs High Dynamic Range (HDR) video data. The HDR video data has contrast ratios from 0 to 100%*N (the N is a number larger than one), for example, from 0 to 1000% and has a brightness exceeding the brightness of the white peak value of an existing Low Dynamic Range (LDR) image. Note that herein the level of 100% corresponds, for example, to a white luminance value of 100 cd/m2. Note that the “cd/m2” indicates “cd/square meter”.

The master monitor 103 a is configured to grade the HDR video data obtained with the HDR camera 102. The master monitor 103 a includes the display luminance levels appropriate to HDR video data, or appropriate for grading HDR video data.

FIG. 3 illustrates the display luminance characteristic of the master monitor 103 a. In the drawing, the input luminance level is shown on the horizontal axis, and the display luminance level is shown on the vertical axis. When the input luminance level is at a reference luminance RL, the display luminance level is at the reference level (%), for example, of 100% that corresponds to the white luminance value of 100 cd/m2. When the input luminance level is at a peak luminance PL, the display luminance level is at the peak level (%).

Note that a threshold luminance CL is newly defined in the present embodiment, and indicates the boundary between the region of which input luminance corresponds to the luminance when the region is displayed in the monitor (CE monitor) on the receiving device, and the region of which luminance depends on the CE monitor. When the monitor input luminance level is at the threshold luminance CL, the display luminance level is at the threshold level (%).

With reference to FIG. 2 again, the HDR opto-electrical transfer unit 103 obtains transmission video data V1 by applying an opto-electrical transfer function for HDR images (an HDR OETF curve) to the HDR video data obtained with the HDR camera 102.

FIG. 4 illustrates an exemplary opto-electrical transfer function (OETF). In the drawing, the input luminance level is shown on the horizontal axis, similarly to the horizontal axis of the display luminance characteristic of the master monitor (see FIG. 3), and a transmission code value is shown on the vertical axis. When the input luminance level is at the reference luminance RL, the transmission code value is at a reference level RP. When the input luminance level is at the peak luminance PL, the transmission code value is at a peak level MP. When the input luminance level is at the threshold luminance CL, the transmission code value is at a threshold level THP.

Note that the range of the transmission code value on the vertical axis corresponds to the input pixel data range (Encoder input pixel data range) of the video encoder 104. For example, when data is encoded in 10-bit encoding, the range is from “64” to “940”, or from “4” to “1019” using the expanded region.

With reference to FIG. 2 again, the video encoder 104 obtains encoded video data by encoding the transmission video data V1, for example, with MPEG-4 AVC encoding, MPEG-2 video encoding, or high Efficiency Video Coding (HEVC) encoding. The video encoder 104 includes a stream formatter (not illustrated) at the latter part to generate a video stream (video elementary stream) including the encoded video data. At that time, the video encoder 104 inserts the luminance conversion acceptable range information about a set region in the screen and the luminance conversion acceptable range information about the entire screen into a layer of the video stream.

(Insertion of Luminance Conversion Acceptable Range Information)

The insertion of the luminance conversion acceptable range information will be described in detail. According to the present embodiment, a regional level mapping SEI message (Regional_Level_mapping SEI message) that is newly defined is inserted in the part of “SEIs” in an access unit (AU).

FIG. 5 illustrates the head access unit of a Group Of Pictures (GOP) when the data is encoded with an HEVC encoding method. FIG. 6 illustrates an access unit other than the head access unit of a GOP when the data is encoded with an HEVC encoding method. When data is encoded with an HEVC encoding method, an SEI message group “Prefix_SEIs” for decoding is placed before slices in which pixel data is encoded, and an SEI message group “Suffix_SEIs” for displaying is placed after the slices. As illustrated in FIGS. 5 and 6, the regional level mapping SEI message is places as an SEI message group “Suffix_SEIs”.

A set region in a screen is set in the unit of pixel or in the unit of block including a predetermined number of pixels. FIG. 7A illustrates an example of set regions set in the unit of pixel. In the illustrated example, a line MR is the ridge of a mountain, and regions R1 and R3 including stars and a region R2 including a neon-light sign are set as set regions. The thing that the creator intends about the regions R1 and R3 is to merely display the twinkle of the stars. Meanwhile, the creator intends to maintain the texture of the neon-light sign in the region R2 although the region R2 has a high luminance.

Each of the set regions has a rectangle shape and is identified with the pixel coordinates on the top left and the pixel coordinates on the bottom right. In other words, the region R1 is identified with pixel coordinates (x1 s, y1 s) on the top left and pixel coordinates (x1 e, y1 e) on the bottom right. The region R2 is identified with pixel coordinates (x2 s, y2 s) on the top left and pixel coordinates (x2 e, y2 e) on the bottom right. The region R3 is identified with pixel coordinates (x3 s, y3 s) on the top left and pixel coordinates (x3 e, y3 e) on the bottom right.

FIG. 7B illustrates an example of set regions set in the unit of block. The screen is divided into a plurality of blocks in horizontal directions and vertical directions. For example, a block has a size of 8*8 pixels, 16*16 pixels, 32*32 pixels, or another size. Each of the blocks is denoted with a block ID. In the illustrated example, regions R11, R12, and R13 are set as set regions.

Each of the set regions has a rectangle shape and is identified with the block ID on the top left and the block ID on the bottom right. In other words, the region R11 is identified with a block ID (ID1 s) on the top left and a block ID (ID1 e) on the bottom right. The region R12 is identified with a block ID (ID2 s) on the top left and a block ID (ID2 e) on the bottom right. The region R13 is identified with a block ID (ID3 s) on the top left and a block ID (ID3 e) on the bottom right.

FIG. 8 illustrates exemplary formation (Syntax) of a regional level mapping SEI message when the set regions are set in the unit of pixel. FIG. 9 illustrates exemplary formation (Syntax) of a regional level mapping SEI message when the set regions are set in the unit of block. FIG. 10 illustrates the contents (Semantics) of the primary information in the exemplary formation.

The “level_mapping_cancel_flag” is flag information of a bit. The “1” indicates the cancellation of the previous state of the level mapping (Level_mapping) message. The “0” indicates that each element is transmitted and the previous state is refreshed with the element.

The eight-bit field of the “coded_data_bit_depth” indicates the bit length of the encoded data, and is, for example, a length of 8 to 14 bits. The 16-bit field of the “reference_white_level” is the input luminance value when the display luminance is at 100% in the master monitor 103 a, namely, the reference luminance RL. The 16-bit field of the “reference_white_level_code_value” indicates the level code value is at the luminance of 100% and the value with the bit precision indicated in the “coded_data_bit_depth”, namely, the reference level RP.

The eight-bit field of the “number_of_regions” indicates the number of set regions in a screen. The 16-bit field of the “global_compliant_threshold_level” is a mapping display threshold for the entire screen. The mapping display threshold is the highest luminance value in CE display that the creator assumes when the creator intends to make the luminance in the CE display correspond to the input luminance. The mapping display threshold is used to indicate that the luminance at a level exceeding the mapping display threshold is displayed depending on the display capacity of the CE monitor. The 16-bit field of the “global_compliant_threshold_level_value” indicates the transmission value (transmission code value) of the mapping display threshold for the entire screen.

The 16-bit field of the “position_start_x” and the 16-bit field of the “position_start_y” indicate the pixel coordinates on the top left identifying a set region. In other words, the “position_start_x” indicates the horizontal start position of a set region with the number of pixels when the top left of an effective display region is set at zero. The “position_start_y” indicates the vertical start position of a set region with the number of pixels when the top left of an effective display region is set at zero.

The 16-bit field of the “position_end_x” and the 16-bit field of the “position_end_y” indicate the pixel coordinates on the bottom right identifying a set region. In other words, the “position_end_x” indicates the horizontal end position of a set region with the number of pixels when the top left of an effective display region is set at zero. The “position_end_y” indicates the vertical end position of a set region with the number of pixels when the top left of an effective display region is set at zero.

The 16-bit field of the “block_start” indicates the block ID on the top left identifying a set region. In other words, the “block_start” indicates the ID (block ID) of a start block from which the set regions are scanned in a direction from the top left to the bottom right block by block. The 16-bit field of the “block_end” indicates the block ID on the bottom right identifying a set region. In other words, the “block_end” indicates the ID (block ID) of an end block to which the set regions are scanned in a direction from the top left to the bottom right block by block. The eight-bit field of the “block_size” indicates the size of the block that is the unit to designate a set region. For example, the block size is designated in the range of 8′8 pixels when the value is “0x01”, the block size is designated in the range of 16′16 pixels when the value is “0x02”, or the block size is designated in the range of 32′32 pixels when the value is “0x03”.

The 16-bit field of the “region_compliant_threshold_level” is a mapping display threshold for the set region. The mapping display threshold is the highest luminance value in the set region in CE display that the creator assumes when the creator intends to make the luminance in the set region in the CE display correspond to the input luminance. The mapping display threshold is used to indicate that the luminance in the set region at a level exceeding the mapping display threshold is displayed depending on the display capacity of the CE monitor. The 16-bit field of the “region_compliant_threshold_level_value” indicates a transmission value (transmission code value) of the mapping display threshold in the set region.

The eight-bit field of the “peak_percentage” indicates a value of the percent of the highest luminance level to 100%. The value is indicated by the creator. For example, the “peak_percentage” of the peak luminance of 1000 cd/m2 is 1000%. In that case, the 100% is indicated as a value 1, and the 1000% is 10 times the 100% and is indicated as a value 10. The 16-bit field of the “peak_percentage_value” indicates the largest code value of the “peak_percentage” when the data is transmitted with the bit precision indicated in the “coded_data_bit_depth”, namely, the peak level MP. For example, when the “peak_percentage” is 1000%, the highest value “1019” in 10-bit transmission indicates the 1000%.

The information of the “global_compliant_threshold_level” and “global_compliant_threshold_level_value” in the regional level mapping SEI message is included in the luminance conversion acceptable range information about the entire screen. The information of the “region_compliant_threshold_level” and “region_compliant_threshold_level_value” is included in the luminance conversion acceptable range information about a set region in the screen. This enables the receiving end to detect the luminance conversion acceptable range information about a set region and detect also the luminance conversion acceptable range information about the other regions from the regional level mapping SEI message.

In such a case, the luminance conversion acceptable range information may be designated picture by picture, scene by scene, or program by program. Note that the type of the OETF (opto-electrical transfer function) to be used is transmitted in video usability information (VUI) to the NAL unit of a sequence parameter set (SPS).

With reference to FIG. 2 again, the system encoder 105 generates the transport stream TS including the video stream VS generated with the video encoder 104. The transmitting unit 106 transmits the transport stream TS through broadcast waves or with packets on a network to the receiving apparatus 200.

The operation of the transmitting apparatus 100 illustrated in FIG. 2 will be described briefly. The HDR video data obtained by the capture with the HDR camera 102 is supplied to the HDR opto-electrical transfer unit 103. The HDR video data obtained with the HDR camera 102 is graded with the master monitor 103 a. The HDR opto-electrical transfer unit 103 obtains the transmission video data V1 by applying the opto-electrical transfer function for HDR images (HDR OETF curve) to the HDR video data. The transmission video data V1 is supplied to the video encoder 104.

The video encoder 104 obtains encoded video data by encoding the transmission video data V1, for example, with MPEG-4 AVC encoding, MPEG-2 video encoding, or HEVC encoding.

The video encoder 104 includes a stream formatter (not illustrated) at the latter part to generate a video stream (video elementary stream) VS including the encoded video data. At that time, the video encoder 104 inserts the luminance conversion acceptable range information about a set region in the screen and the luminance conversion acceptable range information about the entire screen into a layer of the video stream.

The video stream VS generated with the video encoder 104 is supplied to the system encoder 105. The system encoder 105 generates an MPEG-2 transport stream TS including the video stream. The transport stream TS is transmitted through broadcast waves or with packets on a network to the receiving apparatus 200 with the transmitting unit 106.

Exemplary Configuration of Receiving Apparatus

FIG. 11 illustrates an exemplary configuration of the receiving apparatus 200. The receiving apparatus 200 includes a control unit 201, a receiving unit 202, a system decoder 203, a video decoder 204, an HDR electro-optical transfer unit 205, a display mapping unit 206, and a CE monitor 207. The control unit 201 includes a Central Processing Unit (CPU) to control the operation of each of the components in the receiving apparatus 200 in accordance with a control program.

The receiving unit 202 receives the transport stream TS through broadcast waves or with packets on a network from the transmitting apparatus 100. The system decoder 203 extracts the video stream (elementary stream) VS from the transport stream TS. The system decoder 203 further extracts various types of information inserted in the layers of the container (transport stream) to transmit the information to the control unit 201.

The video decoder 204 decodes the video stream VS extracted with the system decoder 203 in a decoding process, and outputs the transmission video data V1. The video decoder 204 extracts the parameter set or SEI message inserted in each of the access units included in the video stream VS to transmit the parameter set or SEI message to the control unit 201.

The control unit 201 recognizes the OETF (opto-electrical transfer function) used on the transmitting end from the designation of the type of OETF in the video usability information (VUI) of the SPS to set an EOTF (electro-optical transfer function), for example, that is inverse to the OETF in the HDR electro-optical transfer unit 205.

The regional level mapping SEI message is one of the SEI messages extracted with the video decoder 204 and transmitted to the control unit 201. The control unit 201 may obtain the information of the “global_compliant_threshold_level” and “global_compliant_threshold_level_value” included in the luminance conversion acceptable range information about the entire screen from the regional level mapping SEI message. The control unit 201 may obtain also the information of the “region_compliant_threshold_level” and “region_compliant_threshold_level_value” included in the luminance conversion acceptable range information about a set region together with the information about the set region from the regional level mapping SEI message.

The HDR electro-optical transfer unit 205 obtains output video data for display an HDR image by applying, for example, an EOTF (electro-optical transfer function) that is inverse to the OETF (opto-electrical transfer function) in the HDR opto-electrical transfer unit 103 of the transmitting apparatus 100 to the transmission video data V1 output from the video decoder 204.

FIG. 12 illustrates an exemplary electro-optical transfer function (EOTF). In the drawing, the transmission code value corresponding to the vertical axis in FIG. 4 is shown on the horizontal axis. The output luminance level (display luminance level) corresponding to the horizontal axis in FIG. 4 is shown on the vertical axis. In the drawing, a solid line a is the EOTF curve. When the transmission code value is at the peak level MP, the output luminance level is PL. When the transmission code value is at the threshold level THP, the output luminance level is CL.

When the highest luminance display capacity of the CE monitor 207 is higher than the highest luminance PL assumed in the master monitor 103 a in that case, the output luminance levels among which the transmission code values are higher than the threshold level THP are assigned to the range up to the display highest luminance level DP1 of the CE monitor 207 in a process in the display mapping unit 206 (luminance increasing process). In the drawing, an alternate long and two short dashes line b is an exemplary luminance conversion process in such a case.

On the other hand, when the highest luminance display capacity of the CE monitor 207 is lower than the highest luminance PL assumed in the master monitor 103 a, the output luminance levels among which the transmission code values are higher than the threshold level THP are assigned to the range up to the display highest luminance level DP2 of the CE monitor 207 in a process in the display mapping unit 206 (luminance decreasing process). In the drawing, an alternate long and short dash line c is an exemplary luminance conversion process in such a case.

With reference to FIG. 11 again, the display mapping unit 206 converts the output luminance levels in the HDR electro-optical transfer unit 205 that exceed the threshold luminance CL in accordance with the highest luminance display capacity of the CE monitor 207, as described above. In that case, the display mapping unit 206 uses the luminance CL appropriate to the set region in the set region of a screen, and uses the luminance CL appropriate to the entire screen in the other regions of the screen.

In such a case, when the transmission code value is at the threshold level THP or lower, in other words, when the output luminance level is equal to or lower than the threshold luminance CL, the luminance is reproduced with fidelity to the luminance at the received level without depending on the CE monitor 207. Thus, for example, the texture of an object is represented correctly in accordance with the creator's intention. The CE monitor 207 displays an HDR image in accordance with the output video data from the display mapping unit 206.

When the highest luminance display capacity DP of the CE monitor 207 is higher than the highest luminance PL assumed in the master monitor 103 a, in other words, when DP>PL holds, the display mapping unit 206 assigns the levels exceeding the threshold luminance CL to the range up to the peak luminance DP with a predetermined algorithm in a luminance increasing process.

Each of FIGS. 13A and 13B illustrates the display luminance characteristic of the CE monitor 207 when DP>PL holds. The characteristic includes the luminance conversion characteristic of the display mapping unit 206. In each of the drawings, the input luminance level is shown on the horizontal axis, and the display luminance level is shown on the vertical axis. FIG. 13A illustrates that the threshold luminance CL is set at a relatively small value CL (1). FIG. 13B illustrates that the threshold luminance CL is set at a relatively large value CL (2).

When the input luminance level is at the threshold luminance CL (1), the display luminance level is at the threshold level THP1. When the input luminance level is at the threshold luminance CL (2), the display luminance level is at the threshold level THP2. In other words, when the input luminance level is at a level up to the threshold luminance CL (1) or CL (2), the display luminance level is at the level that the creator intends. When the input luminance level is at the peak luminance PL, the display luminance level is at the peak level DP of the CE monitor 207. In other words, when the input luminance level is between the threshold luminance CL (1) or CL (2) and the peak luminance PL, a luminance increasing process is performed as denoted with a solid line L1 or L2.

When the highest luminance display capacity DP of the CE monitor 207 is lower than the highest luminance PL assumed in the master monitor 103 a, in other words, when DP<PL holds, the display mapping unit 206 assigns the levels exceeding the threshold luminance CL to the range up to the peak luminance DP with a predetermined algorithm in a luminance decreasing process.

Each of FIGS. 14A and 14B illustrates the display luminance characteristic of the CE monitor 207 when DP<PL holds and the highest luminance display capacity DP is relatively high. The display luminance characteristic includes the luminance conversion characteristic of the display mapping unit 206. In each of the drawings, the input luminance level is shown on the horizontal axis, and the display luminance level is shown on the vertical axis.

FIG. 14A illustrates that the threshold luminance CL is set at a relatively small value CL (3). FIG. 14B illustrates that the threshold luminance CL is set at a relatively large value CL (4). When the input luminance level is at the threshold luminance CL (3), the display luminance level is at the threshold level THP3. When the input luminance level is at the threshold luminance CL (4), the display luminance level is at the threshold level THP4. In other words, when the input luminance level is at a level up to the threshold luminance CL (3) or CL (4), the display luminance level is at the level that the creator intends. When the input luminance level is at the peak luminance PL, the display luminance level is at the peak level DP of the CE monitor 207. In other words, when the input luminance level is between the threshold luminance CL (3) or CL (4) and the peak luminance PL, a luminance decreasing process is performed as denoted with a solid line L31 or L41.

Each of FIGS. 15A and 15B illustrates the display luminance characteristic of the CE monitor 207 when DP<PL holds and the highest luminance display capacity DP is relatively low. The display luminance characteristic includes the luminance conversion characteristic of the display mapping unit 206. In each of the drawings, the input luminance level is shown on the horizontal axis, and the display luminance level is shown on the vertical axis.

FIG. 15A illustrates that the threshold luminance CL is set at a relatively small value CL (3) and the threshold level THP3 is lower than the peak level DP of the CE monitor 207. When the input luminance level is at the threshold luminance CL (3), the display luminance level is at the threshold level THP3. In other words, when the input luminance level is at a level up to the threshold luminance CL (3), the display luminance level is at the level that the creator intends. When the input luminance level is at the peak luminance PL, the display luminance level is at the peak level DP of the CE monitor 207. In other words, when the input luminance level is between the threshold luminance CL (3) and the peak luminance PL, a luminance decreasing process is performed as denoted with a solid line L32.

FIG. 15B illustrates that the threshold luminance CL is set at a relatively large value CL (4) and the threshold level THP4 is higher than the peak level DP of the CE monitor 207. When the input luminance level is at a value CLa smaller than the threshold luminance CL (4), the display luminance level is at the peak level DP of the CE monitor 207. In other words, when the input luminance level is at a level up to the threshold luminance CLa, the display luminance level is at the level that the creator intends in such a case. When the input luminance level is between the value CLa and the peak luminance PL, the display luminance level is, for example, at the peak level DP of the CE monitor 207 as denoted with solid line L42. Note that a display luminance conversion may be performed in such a case so as to vary the display luminance level smoothly on the high luminance side, for example, as denoted with a dashed line L42′.

The operation of the receiving apparatus 200 illustrated in FIG. 11 will be described briefly. The receiving unit 202 receives the transport stream TS from the transmitting apparatus 100 through broadcast waves or with packets on a network. The transport stream TS is supplied to the system decoder 203. The system decoder 203 extracts the video stream (elementary stream) VS from the transport stream TS.

The video stream VS extracted with the system decoder 203 is supplied to the video decoder 204. The video decoder 204 decodes the video stream VS extracted with the system decoder 203 in a decoding process to obtain the transmission video data V1. The video decoder 204 extracts the parameter set or SEI message inserted in each of the access units included in the video stream VS to transmit the extracted parameter set or SEI message to the control unit 201.

The control unit 201 obtains the information of “global_compliant_threshold_level” and “global_compliant_threshold_level_value” included in the luminance conversion acceptable range information about the entire screen from the regional level mapping SEI message. The control unit 201 further obtains the information of “region_compliant_threshold_level” and “region_compliant_threshold_level_value” included in the luminance conversion acceptable range information about each of the set regions together with the information about the set region from the regional level mapping SEI message.

The transmission video data V1 obtained with the video decoder 204 is supplied to the HDR electro-optical transfer unit 205. The HDR electro-optical transfer unit 205 obtains output video data for displaying an HDR image by applying, for example, an EOTF (electro-optical transfer function) that is inverse to the OETF (opto-electrical transfer function) of the HDR opto-electrical transfer unit 103 in the transmitting apparatus 100 to the transmission video data V1. The output video data is supplied to the display mapping unit 206.

The display mapping unit 206 coverts the output luminance levels exceeding the luminance CL in the HDR electro-optical transfer unit 205 in accordance with the highest luminance display capacity of the CE monitor 207. At that time, the display mapping unit 206 uses the luminance CL appropriate to the set region in the set regions of the screen, and uses the luminance CL appropriate to the entire screen in the other regions of the screen. The output video data is supplied from the display mapping unit 206 to the CE monitor 207. The CE monitor 207 displays an HDR image.

As described above, the transmission video data V1 obtained from opto-electrical transferred HDR video data is transmitted together with the luminance conversion acceptable range information about the set region in the screen in the transmitting and receiving system 10 illustrated in FIG. 1. Thus, the luminance of each of the set regions is independently converted in the luminance conversion acceptable range in accordance with the display luminance capacity of the CE monitor 207 on the receiving end. This can excellently reproduce the luminance atmosphere that the creator intends.

In the example in FIG. 7A, even when the luminance of the stars in the regions R1 and R3, and the neon-light sign in the region R2 are set at the same luminance level, the threshold level CL of the regions R1 and R3 is lower than the luminance level and the threshold level CL of the region R2 is higher than the luminance level.

In such a case, the luminance of the stars is included in the luminance conversion acceptable range and is to be display mapped, while the luminance of the neon-light sign is not included in the luminance conversion acceptable range and is not to be display mapped. Thus, the creator intentions to merely display the twinkle of the stars in the regions R1 and R3 and to maintain the texture of the neon-light sign even in the region R2 having a high luminance can excellently be reproduced on the receiving end.

The transmission video data V1 is transmitted together with the luminance conversion acceptable range information about the entire screen in addition to the luminance conversion acceptable range information about the set region in the screen in the transmitting and receiving system 10 illustrated in FIG. 1. This enables the receiving end to convert the luminance of the regions other than the set region in the screen in accordance with the luminance conversion acceptable range information about the entire screen in a luminance conversion process.

2. Variation

Note that, according to the embodiment, the luminance conversion acceptable range information about a predetermined number of set regions and the luminance conversion acceptable range information about the entire screen is placed in the regional level mapping SEI messages to transmit the information to the receiving end. However, only the luminance conversion acceptable range information about a predetermined number of set regions may be transmitted to the receiving end. In such a case, for example, prescribed luminance conversion acceptable range information is used in the regions other than the set regions in the screen on the receiving end.

The HDR electro-optical transfer unit 205 performs an electro-optical transfer process while the display mapping unit 206 performs a luminance conversion process in accordance with the highest luminance display capacity of the CE monitor 207 in the receiving apparatus 200 according to the embodiment. However, reflecting the luminance conversion characteristic on the electro-optical transfer function (EOTF) enables the HDR electro-optical transfer unit 205 to singly perform an electro-optical process and a luminance conversion process simultaneously.

The transmitting and receiving system 10 according to the embodiment includes the transmitting apparatus 100 and the receiving apparatus 200. However, the configuration of the transmitting and receiving system to which the present technology may be applied is not limited to the embodiment. For example, a television 200 may include a set top box 200A and a monitor 200B connected to each other via a digital interface such as a High-Definition Multimedia Interface (HDMI) as illustrated in FIG. 16. Note that the “HDMI” is a registered trademark.

In such a case, the set top box 200A may determine the highest luminance level of the monitor 200B in accordance with the information in EDID of the monitor 200B while obtaining the information via the HDMI when the set top box 200A performs a display mapping process. Alternatively, when the monitor 200B performs a display mapping process, the set top box 200A and the monitor 200B can share the information by defining the level mapping SEI message, the type of EOTF, and the information about VUI in meta data such as the “Vender Specific Info Frame”.

According to the embodiment, the transport stream (MPEG-2 TS) is used as a container. However, the present technology does not limit the transport stream to the transport stream TS. Even when another packet, for example, in ISO BMFF or MMT is used, the layers of video data can be implemented in the same manner as according to the embodiment.

Thus, the present technology may be applied to a system that distributes data to a receiving terminal via a network such as the Internet as well. When data is distributed via the Internet, a container in MP4 or another format is often used to distribute the data. In other words, containers in various format, for example, a transport stream (MPEG-2 TS) used as a digital broadcast standard, or MP4 used for distribution via the Internet may be used for the container according to the present technology.

The present technology can also be adopted the following configuration.

(1) A transmitting apparatus including:

a processing unit configured to obtain transmission video data by applying a predetermined opto-electrical transfer function to input video data, and

a transmitting unit configured to transmit the transmission video data together with luminance conversion acceptable range information about a set region in a screen.

(2) The transmitting apparatus according to (1), wherein the transmitting unit transmits the transmission video data together with luminance conversion acceptable range information about an entire screen in addition to the luminance conversion acceptable range information about the set region in the screen.

(3) The transmitting apparatus according to (1) or (2), wherein the set region in the screen is set in a unit of pixel or in a unit of block including a predetermined number of pixels.

(4) The transmitting apparatus according to any of (1) to (3), further including:

an information inserting unit configured to insert the luminance conversion acceptable range information into a layer of a video stream obtained by encoding the transmission video data,

wherein the transmitting unit transmits the video stream.

(5) A transmitting method including:

obtaining transmission video data by applying a predetermined opto-electrical transfer function to input video data, and

transmitting, with a transmitting unit, the transmission video data together with luminance conversion acceptable range information about a set region in a screen.

(6) A receiving apparatus including:

a receiving unit configured to receive transmission video data obtained by applying a predetermined opto-electrical transfer function to input video data together with luminance conversion acceptable range information about a set region in a screen; and

a processing unit configured to obtain output video data by applying an electro-optical transfer function corresponding to the predetermined opto-electrical transfer function to the transmission video data, and converting luminance of the transmission video data in a luminance conversion process in accordance with the luminance conversion acceptable range information.

(7) The receiving apparatus according to (6), wherein the receiving unit receives the transmission video data together with luminance conversion acceptable range information about an entire screen in addition to the luminance conversion acceptable range information about the set region in the screen, and

the processing unit performs a luminance conversion process in a region other than the set region in the screen in accordance with the luminance conversion acceptable range information about the entire screen.

(8) The receiving apparatus according to (6) or (7), wherein the set region in the screen is set in a unit of pixel or in a unit of block including a predetermined number of pixels.

(9) The receiving apparatus according to any of (6) to (8),

wherein the receiving unit receives video stream obtained by encoding the transmission video data, and

the luminance conversion acceptable range information is inserted in a layer of the video stream.

(10) A receiving method including:

receiving, with a receiving unit, transmission video data obtained by applying a predetermined opto-electrical transfer function to input video data together with luminance conversion acceptable range information about a set region in a screen; and

obtaining output video data by applying an electro-optical transfer function corresponding to the predetermined opto-electrical transfer function to the transmission video data, and converting luminance of the transmission video data in a luminance conversion process in accordance with the luminance conversion acceptable range information.

(11) A transmitter comprising:

circuitry configured to implement

-   -   a processor that applies a predetermined opto-electrical         transfer function to input image data to obtain output image         data, and     -   store the output image data in association with         context-determined luminance conversion range information         regarding a sub-region of an image to be displayed.

(12) The transmitter of 11, wherein the circuitry is further configured to transmit the output image data in association with the context-determined luminance conversion range information.

(13) The transmitter of 11, wherein the output image data is video data, and the sub-region being a smaller region than a region covered by an entirety of a video frame.

(14) The transmitter according to 12, wherein the transmitter transmits the output image data together with the context-determined luminance conversion range information about an entire image area of the image to be displayed in addition to the context-determined luminance conversion range information about the sub-region of the image to be displayed.

(15) The transmitter according to 11, wherein the sub-region is defined in units of a pixel or in a pixel block that includes a predetermined number of pixels.

(16) The transmitter according to 12, wherein the circuitry is further configured to insert the context-determined luminance conversion range information into a layer of a video stream obtained by encoding the output image data, and transmit the video stream via the transmitter.

(17) A transmitting method comprising:

-   -   applying with circuitry a predetermined opto-electrical transfer         function to input image data to obtain output image data, and     -   store the output image data in association with a         context-determined luminance conversion range information         regarding a sub-region of an image to be displayed.

(18) The transmitting method of 17, further comprising:

-   -   inserting the context-determined luminance conversion range         information into a layer of a video stream obtained by encoding         the output image data, and transmitting the video stream.

(19) The transmitting method of 17, wherein the image data is video data, and the sub-region being a smaller region than a region covered by an entirety of a video frame of a video image to be displayed.

(20) A receiver comprising:

-   -   circuitry configured to     -   receive image data from another device that applied a         predetermined opto-electrical transfer function to input image         data and stored output image data in association with a         context-determined luminance conversion range for a sub-region         of an image to be displayed, and     -   apply an electro-optical transfer function, which corresponds to         the predetermined opto-electrical transfer function, to the         output image data received from the another device, and convert         a luminance of the output image data received from the another         device in a luminance conversion process in accordance with the         context-determined luminance conversion range information.

(21) The receiver of 20, wherein the output image data is video data, and the sub-region being a smaller region than a region covered by an entirety of a video frame.

(22) The receiver according to 20, wherein the circuitry is further configured to receive the output image data together with context-determined luminance conversion range information for an entire image area in addition to the context-determined luminance conversion range information for the sub-region of the entire image area, and

-   -   the circuitry is further configured to perform a luminance         conversion process in a region other than the sub-region in         accordance with the context-determined luminance conversion         range information for the entire image area.

(23) The receiver according to 22, wherein the sub-region is defined in units of a pixel or in a pixel block that includes a predetermined number of pixels.

(24) The receiver according to 22,

-   -   wherein the circuitry is configured to receive a video stream         that includes the output image data, and     -   the context-determined luminance conversion range information.

(25) A receiving method comprising:

-   -   receiving, with a receiver, image data from another device that         applied a predetermined opto-electrical transfer function to         input image data and stored the image data in association with a         context-determined luminance conversion range for a sub-region         of an image to be displayed; and     -   obtaining with circuitry output video data by applying an         electro-optical transfer function corresponding to the         predetermined opto-electrical transfer function to the image         data, and converting luminance of the image data in a luminance         conversion process in accordance with the context-determined         luminance conversion range information.

(26) The method of 25, wherein the image data is video data, and the sub-region being a smaller region than a region covered by an entirety of a video frame.

(27) The method according to 25, further comprising:

-   -   receiving the image data together with context-determined         luminance conversion range information for an entire image area         in addition to the context-determined luminance conversion range         information for the sub-region of the entire image area, and     -   performing with the circuitry a luminance conversion process in         a region other than the sub-region in accordance with the         context-determined luminance conversion range information for         the entire image area.

(28) The method according to 25, wherein the sub-region is defined in units of a pixel or in a pixel block that includes a predetermined number of pixels.

(29) The method according to 25,

-   -   further comprising:     -   receiving a video stream that includes the image data, the         context-determined luminance conversion range information.

According to a primary feature of the present technology, the transmission video data obtained from electro-optical transferred HDR video data is transmitted together with the luminance conversion acceptable range information about the set regions in the screen, and the luminance of each of the set regions in a screen is independently converted only in the luminance conversion acceptable range on the receiving end. This can excellently reproduce the luminance atmosphere that the creator intends (See FIGS. 5 to 9).

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

REFERENCE SIGNS LIST

-   10, 10A Transmitting and receiving system -   100 Transmitting apparatus -   101 Control unit -   102 HDR camera -   103 HDR opto-electrical transfer unit -   103 a Master monitor -   104 Video encoder -   105 System encoder -   106 Transmitting unit -   200 Receiving apparatus -   200A Set top box -   200B Monitor -   201 Control unit -   202 Receiving unit -   203 System decoder -   204 Video decoder -   205 HDR electro-optical transfer unit -   206 Display mapping unit -   207 CE monitor 

The invention claimed is:
 1. A transmitter, comprising: circuitry configured to: apply a predetermined opto-electrical transfer function to input image data to obtain transmission image data; generate a control message that includes first context-determined luminance conversion range information for a sub-region of an image represented by the transmission image data, the first context-determined luminance conversion range information including a first threshold luminance level, a luminance level within the sub-region of the image is subject to a first conversion processed by a receiver regardless of a display capability of the receiver when the luminance level is not greater than the first threshold luminance level, and subject to a second conversion processed by the receiver according to the display capability of the receiver when the luminance level is greater than the first threshold luminance level; and transmit the transmission image data and the control message to the receiver.
 2. The transmitter of claim 1, wherein the transmission image data is video data, and the sub-region is a smaller region than a region covered by an entirety of a video frame.
 3. The transmitter according to claim 1, wherein the circuitry is configured to generate the control message that includes second context-determined luminance conversion range information for an entirety of the image represented by the transmission image data, the second context-determined luminance conversion range information including a second threshold luminance level, another luminance level within a region of the image represented by the transmission image data other than the sub-region is subject to a third conversion processed by the receiver regardless of the display capability of the receiver when the another luminance level is not greater than the second threshold luminance level, and subject to a fourth conversion processed by the receiver according to the display capability of the receiver when the another luminance level is greater than the second threshold luminance level.
 4. The transmitter according to claim 1, wherein the sub-region is indicated in the control message by specifying pixels of the sub-region or by specifying a predetermined block of pixels.
 5. The transmitter according to claim 1, wherein the circuitry is further configured to: insert the control message that includes the first context-determined luminance conversion range information into a layer of a video stream obtained by encoding the transmission image data; and transmit the video stream to the receiver.
 6. A transmitting method, comprising: applying a predetermined opto-electrical transfer function to input image data to obtain transmission image data; generating, by circuitry of a transmitter, a control message that includes context-determined luminance conversion range information for a sub-region of an image represented by the transmission image data, the context-determined luminance conversion range information including a threshold luminance level, a luminance level within the sub-region of the image is subject to a first conversion processed by a receiver regardless of a display capability of the receiver when the luminance level is not greater than the threshold luminance level, and subject to a second conversion processed by the receiver according to the display capability of the receiver when the luminance level is greater than the threshold luminance level; and transmitting, by the circuitry, the transmission image data and the control message to the receiver.
 7. The transmitting method of claim 6, further comprising: inserting the control message that includes the context-determined luminance conversion range information into a layer of a video stream obtained by encoding the transmission image data; and transmitting the video stream to the receiver.
 8. The transmitting method of claim 6, wherein the transmission image data is video data, and the sub-region is a smaller region than a region covered by an entirety of a video frame of a video frame.
 9. A receiver, comprising: circuitry configured to: receive transmission image data and a control message from another device, the transmission image data is generated by applying a predetermined opto-electrical transfer function to input image data, and the control message includes first context-determined luminance conversion range information for a sub-region of an image represented by the transmission image data, the first context-determined luminance conversion range information including a first threshold luminance level; apply an electro-optical transfer function, which corresponds to the predetermined opto-electrical transfer function, to the transmission image data received from the another device to obtain output image data; perform a luminance conversion process on the output image data in accordance with the first context-determined luminance conversion range information to obtain converted image data, including performing a first conversion on a luminance level within the sub-region of the image regardless of a display capability of the receiver when the luminance level is not greater than the first threshold luminance level, and performing a second conversion on the luminance level within the sub-region of the image according to the display capability of the receiver when the luminance level is greater than the first threshold luminance level; and display the image on a display according to the converted image data.
 10. The receiver of claim 9, wherein the transmission image data is video data, and the sub-region is a smaller region than a region covered by an entirety of a video frame.
 11. The receiver according to claim 9, wherein the circuitry is configured to: receive the control message that includes second context-determined luminance conversion range information for an entirety of the image represented by the transmission image data, the second context-determined luminance conversion range information including a second threshold luminance level; and perform the luminance conversion process on the output image data, including performing a third conversion on another luminance level within a region of the image other than the sub-region regardless of the display capability of the receiver when the another luminance level is not greater than the second threshold luminance level, and performing a fourth conversion on the another luminance level within the region of the image other than the sub-region according to the display capability of the receiver when the another luminance level is greater than the second threshold luminance level.
 12. The receiver according to claim 9, wherein the sub-region is indicated in the control message by specifying pixels of the sub-region or by specifying a predetermined block of pixels.
 13. The receiver according to claim 11, wherein the circuitry is configured to receive a video stream; and extract the transmission image data and the first context-determined luminance conversion range information from the received video stream.
 14. A receiving method, comprising: receiving, by circuitry of a receiver, transmission image data and a control message from another device, the transmission image data is generated by applying a predetermined opto-electrical transfer function to input image data, and the control message includes first context-determined luminance conversion range information for a sub-region of an image represented by the transmission image data, the first context-determined luminance conversion range information including a first threshold luminance level; applying an electro-optical transfer function, which corresponds to the predetermined opto-electrical transfer function, to the transmission image data received from the another device to obtain output image data; performing a luminance conversion process on the output image data in accordance with the first context-determined luminance conversion range information to obtain converted image data, including performing a first conversion on a luminance level within the sub-region of the image regardless of a display capability of the receiver when the luminance level is not greater than the first threshold luminance level, and performing a second conversion on the luminance level within the sub-region of the image according to the display capability of the receiver when the luminance level is greater than the first threshold luminance level; and displaying the image on a display according to the converted image data.
 15. The method of claim 14, wherein the transmission image data is video data, and the sub-region is a smaller region than a region covered by an entirety of a video frame.
 16. The method according to claim 14, further comprising: receiving the control message that includes second context-determined luminance conversion range information for an entirety of the image represented by the transmission image data, the second context-determined luminance conversion range information including a second threshold luminance level; and performing the luminance conversion process on the output image data, including performing a third conversion on another luminance level within a region of the image other than the sub-region regardless of the display capability of the receiver when the another luminance level is not greater than the second threshold luminance level, and performing a fourth conversion on the another luminance level within the region of the image other than the sub-region according to the display capability of the receiver when the another luminance level is greater than the second threshold luminance level.
 17. The method according to claim 14, wherein the sub-region is indicated in the control message by specifying pixels of the sub-region or by specifying a predetermined block of pixels.
 18. The method according to claim 14, further comprising: receiving a video stream; and extracting the transmission image data and the first context-determined luminance conversion range information from the received video stream. 